Multi Generators - One neutral grounded 1

[NickParker]

When generators are operating in parallel , neutral contactors are interlocked with generator breakers to ensure that only one generator's neutral is connected to earth to eliminate circulating currents. What happens if a Line to ground fault occurs within a Generator whose neutral is not grounded?

Do the other unfaulted generators trip? or only the faulted generator gets tripped?

 

[waross]

The differential trip will shut it down.
Note that for an internal fault, it is often necessary to stop the prime mover as well as eliminating any back fed current.
Without a differential trip, back fed current from the other sets may trip the generator breaker.
It depends, but the fault may not be at the line end of the winding.
As well, it depends on how the AVR sensing is connected and f the set has a PMG.
It would not be unusual for a smaller set to run to the destruction of part of the core as a result of an internal fault.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[RRaghunath]

Does the generator have directional earth fault protection looking towards the generator?
If true, this protection will isolate the faulty generator instantaneously (or may a short time delay).
The generator whose neutral is earthed also will have zero sequence current but the protection will not operate as the current is flowing away from the generator.
If the fault current is large enough, generator differential protection (if provided) will operate as Mr. Bill mentioned.
I suppose the generators are LV and the neutral is solidly earthed.

 

[slavag]

Directional earth fault protection is used. Toward to to the generator.